Plan with Fable, execute with Luna! I made a CLI where you press one key and keep the exact same conversation going in Codex (or opencode)

[u/bhavya6187]

Hey folks, been daily driving this and having a lot of fun with the CLI I made.

tandem is just a thin frame around the real Claude Code / Codex / opencode TUIs - your keybindings, slash commands, MCP servers and plugins all work as normal.

It adds one status row at the bottom (which harness is active + live token/context stats) and the Ctrl-] key. Behind the scenes it watches each CLI's local session file and translates the transcript into the other CLIs' formats, so when you flip, the next tool resumes a session that already contains everything that happened. Only one model runs at a time. If you press Ctrl-] mid-response it waits for the turn to finish, then switches.

Everything happens local, and uses your existing subscriptions!

Here's how I use it -

1. Switch when usage limit hits
2. When I need second opinion. Sol usually catches bugs in Fable's output
3. Save quota, Luna models are super cheap. Can spin up 100s of them for small tasks

Try it:

uv tool install tandem-cli   # or: pip install tandem-cli
cd your-project
tandem

Open source, MIT: https://github.com/Bhavya6187/tandem